Typical integrated circuit device goals are to increase integrated circuit performance and to increase transistor density (i.e., transistors per unit area) at minimum circuit power. To minimize power, many integrated circuits are made in the complementary insulated gate field effect transistor (FET) technology known as complementary metal oxide semiconductor (CMOS). A typical CMOS circuit includes paired complementary devices, i.e., an n-type FET (NFET) paired with a corresponding p-type FET (PFET), usually gated by the same signal. A CMOS inverter, for example, is a PFET and NFET pair that are series connected between a power supply voltage and ground (GND), and both gated by the same input signal. Since the pair of devices have operating characteristics that are, essentially, opposite each other, when one device (e.g., the NFET) is on and conducting, the other device (the PFET) is off, not conducting and, vice versa. The switch is open, i.e., the device is off, when the magnitude of the gate to source voltage (Vgs) is less than that of some threshold voltage (VT). So, ideally, an NFET is off when its Vgs is below VT, and the NFET is on and conducting current above VT. Similarly, a PFET is off when its gate voltage, Vgs, is above its VT, i.e., less negative, and on below VT.
Typically, to increase transistor density, the transistor channel is scaled along with the gate pitch which tends to increase the parasitic series resistance in devices due to the decreasing contact size and the scaled implanted junction depths. Series resistance may be represented by various components, one of which is the silicide to doped silicon interface resistance referred to as interface resistance, RINT, where a source and drain junction region contain a silicide. RINT will continue to effect the total transistor resistance particularly for NFETs or NMOS devices and will tend to get worse with continued scaling due to the fixed barrier height from Fermi level pinning at the silicide-silicon interface in the middle of the silicon bandgap.